-met is a suffix to emphazise a few pronouns, but not all pronouns.
We can translate '-met' with 'self, but actually it is not translatable!
In Latin it has not really the meaning of 'self', that's why the forms with m--met can be emphazised even more by 'ipse'.

The classical form is not 'tumet', but 'tute', and not 'semet', but 'sese'. This last one mostly is the best known of the series.

So if any one asks you if you want a candy and your sister yells 'ego', then your brother can even do better with 'egomet'. But you can do better than both of them by yelling 'egomet ipse'.